The present invention relates to an electronic musical instrument having a stereophonic function to impart an acoustic image to a produced musical sound.
Conventionally, one type of electronic musical instrument having the stereophonic function utilizes a stereo tone generator which undergoes stereo sampling of a waveform for obtaining stereophonic location and wideness of an acoustic image dependent on a tone pitch. For this, the stereo tone generator stores a pair of waveforms for an individual musical tone, thereby requiring a relatively large capacity waveform memory. Another type of conventional electronic musical instrument, such as an electronic piano of moderate price utilizes a monaural tone generator which stores a single tone waveform, while a pseudo-stereo circuit such as a comb filter circuit is adapted to process the generated monaural tone signal to impart thereto stereophonic wideness or spread of an acoustic image. However, the obtained acoustic image is rather monotonous in that the spread and location of the acoustic image is uniform for different tone pitches, thereby disadvantageously producing an unnatural sound. In contrast, an acoustic piano generates in a left zone a relatively low pitch tone which is resonated by a vibration plate to thereby emit a spread piano sound. Further, a relatively high pitch tone is generated in a right zone of the acoustic piano, and is directly emitted to dominate the resulting piano sound. Therefore, the high pitch piano sound has a definite location originating from the right zone of the piano. In contrast, the conventional electronic musical instrument having the monaural tone generator has a drawback that such a realistic acoustic field of a natural piano instrument cannot be realized.